I'm using dynamic light scattering to measure size of TiO2 nano-particle, and I need the absorption of TiO2. I looked up many literature, but I only found a spectrum of the absorption, no accurate numbers. I only know it's really small.
Is there any handbook or publication I can look up for the number?
There is an online resource for several materials at http://luxpop.com/ and TiO2 (rutile) is listed there. For 20C and 633nm the values n=2.42 and k-0.0006 are provided with a reference. So that should provide a decent first guess for the values.
For dynamic light scattering keep in mind that the z-average (=average size based on cumulants fit), polydispersity index (=indication of the relative width of an assumed Gaussian distribution), and intensity based particle size distribution are all independent of the refractive index of the material. It is only when you want to convert to volume/mass or number distributions that the refractive properties of the scattering objects come into effect. In practical applications, as long as your particles are 100nm or less, the influence of the refractive index and the absorption will be very small. You can test this yourself by reanalyzing data with changed refractive index values to observe the effect.
If your TiO2 nanoparticles are less than 100nm there should be no problem using the rutile values.
We are characterizing TiO2 particles in the UV range, where their absorption is significant. But, DLS systems use laser in the visible range (633, 532nm)... where the absorption of TiO2 (rutile or not) is extremely weak and usually negligible. You can check in the "Optical Data from Sopra SA - Software Spectra"
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